The present invention relates to a sewing machine including a presser foot for pressing a fabric on a feed dog which operates through slots on a needle plate. The sewing machine forms a chain stitch by collaboration with a needle reciprocating vertically (penetrating up and down) through the presser foot and needle plate and a looper which traverses on makes elliptical path laterally and longitudinally beneath the needle plate. More particularly, in a sewing machine of this kind, the present invention relates to an apparatus for cutting off a thread chain formed consecutively with the tail end of a seam on a fabric, and for sewing the cut thread chain connected to the needle into the seam of the initial end on the fabric to be sewn next, thereby preventing looseness (ravel) of the thread at the beginning end of sewing.
In a lock stitch sewing machine, to prevent ravel of thread from the initial end or tail end of a seam, "turn sewing (reverse stitch)" is done, but in a chain stitch sewing machine such as an overedge sewing machine, since the seam cannot be formed while moving back the fabric, generally, the thread chain formed consecutively with the tail end of sewing on the fabric is held in front of the sewing area, and the thread chain is sewn into the overedge seam together with the start of sewing of the next fabric. As disclosed, for example, in Japanese Laid-open Patent No. 54-16257 (U.S. Pat. No. 4,175,500), in a safety seam sewing machine for forming a double chain stitch inside the fabric along the overedge seam, the thread chains of the overedge seam and the double chain stitch are both held in front of the sewing area before the start of sewing, and they are sewn into the overedge seam to be formed in the fabric together with the start of sewing.
In such double chain stitch sewing machines, incidentally, the thread chain is pulled and turned to the front of the sewing area by a manual operation, and its end is held by a gripping tool called a gripper. It, therefore, requires a complicated job to treat a thread chain, which is likely to lower sewing efficiency. In a sewing machine which has an overedge needle located backwardly of a double chain stitch needle relative to the direction of movement of the material, one thread chain of an overedge seam or a double chain stitch will loosen and therefore it may be difficult to sew the loosened chain into the overedge seam.